Supramolecular helical architectures dictated by folded and extended conformations of the amino acid in ternary CuII/diamine/racemic amino acid complexes

Article abstract of DOI:10.1002/ejic.200600967

The ternary Cu^II complexes [Cu(D,L-phe)(bpy)]·(ClO ₄) (1), [Cu(D,L-phe)(phen)(H₂O)]·ClO ₄·H₂O (2), and [Cu(L-phe)-(bpy)(H ₂O)]·ClO₄·H₂O (3) (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) adopt helical structures in the crystal state, as determined by an X-ray structural analysis. The supramolecular helical assembly of these complexes was also investigated by single-crystal X-ray crystallography. The complexes derived from racemic amino acids (1 and 2) undergo spontaneous resolution in the solid state to form separate helical chains of the ternary complex that carry a single enantiomer of the amino acid. In the case of complex 1, the two helical chains resulting from the L- and D-phe complexes bear opposite chirality, which means that the bulk crystalline sample is racemic. In contrast, the two helical chains generated by L- and D-phe complexes in 2 have the same twist and pack together in a right-handed assembly. The (P)/(M) handedness of the helical chains is dictated by the conformational chirality (λ/δ) of the chelate rings of the D/L-amino acids. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.